BIP39 mnemonic phrases are not randomly "selected words", but rather:
The wallet uses high-quality random numbers (entropy).
The entropy is divided into several segments, each 11 bits.
Each segment is mapped to a word from the BIP39 fixed list of 2048 words.
Since each segment is independently random, it's possible for different segments to map to the same word → the appearance of duplicate words is normal.
Probability of Duplicates
Since each selection is made randomly from the same list of 2048 words, it's theoretically possible to draw the same word, which would result in duplicates.
This is similar to "drawing cards": drawing 12/24 times from a deck of 2048 cards, drawing a duplicate card is completely normal.
Mnemonic Phrase Length | Probability of "at least one duplicate word" |
12 Words | ≈ 3% (approx. 1/33) |
24 Words | ≈ 12% (approx. 1/8) |
In other words: for a 24-word phrase, the probability of duplicates is ≈ 1 in 8 generations.
The security of a mnemonic phrase comes from the underlying number of random entropy bits (128 / 256 bits), not from whether the words are duplicates. Even if duplicates appear, the randomness remains intact. Duplicates are merely a "natural manifestation of randomness" and do not weaken security.
Why is the Randomness of OneKey Hardware Wallet Mnemonic Phrases Reliable?
OneKey's Advantages:
✅ Open Source: Firmware and code are publicly auditable, ensuring transparent security.
✅ Uses EAL6+ Security Chip
Provides True Random Numbers (TRNG) at the hardware level.
Entropy quality is certified and evaluated.
Additionally, if you are not satisfied with the generated mnemonic phrase, you can regenerate a completely new set of mnemonic phrases on your OneKey hardware wallet and back them up properly.